Abstract. A series of cross-slope transects were occupied in 2013 and 2015 that extended eastward from St. Anna Trough to the Lomonosov Ridge. High-resolution physical and chemical observations collected along these transects revealed fronts in the potential temperature and the stable oxygen isotopic ratio (δ18O) that were observed north of Severnaya Zemlya (SZ). Using linear regressions, we describe mixing regimes on either side of the front that characterize a transition from a seasonal halocline to a permanent halocline. This transition describes the formation of lower halocline water (LHW) and the cold halocline layer via a mechanism that has been previously postulated by Rudels et al. (1996). Initial freshening of Atlantic Water (AW) by sea-ice meltwater occurs west of SZ, whereas higher influences of meteoric water and brine result in a transition to a separate mixing regime that alters LHW through mixing with overlying waters and shifts the characteristic temperature–salinity bend from higher (34.4 ≤ S ≤ 34.5) toward lower (34.2 ≤ S ≤ 34.3) salinities. These mixing regimes appear to have been robust since at least 2000.

High-resolution measurements of temperature, salinity, and the stable oxygen isotope ratio of seawater were collected along the slopes of the Barents, Kara, and Laptev seas during late summer of 2013 and 2015. Two separate mixing regimes were identified that describe the initial and final stages of halocline water formation. The linear regressions defining the mixing regimes appear to be stable despite the dramatic environmental changes observed over the Arctic Ocean over the past two decades.